Cooling and annealing of glass in strip form and apparatus therefor



Jan. 21, 1930. E. B. LE MARE I COOLING AND ANNEALING OF GLASS IN STRIPFORM AND APPARATUS THEREFOR Filed Nov. 12. 924

Patented Jan. 21, 1930 UNITED 'STATES ,PATENT OFFICE ERNEST BRISTOW LEMARE, OF ST. HELENS, ENGLAND, ASSIGNOE TO PILKINGTON BROTHERS LIMITED,OF LIVERPOOL, ENGLAND, A BRITISH COMPANY COOLING AND ANNEALING OF GLASSIN STRIP FOBM AND APPABATUS THEREOR Application filed November 12, 1924,Serial No. '749,421, and in Great Britain November 19, 1923.

This invention relates to the cooling and annealing of glass in stripform and apparatus therefor and has for its object to prevent thewarpingofthe strip and to maintain it flat during cooling'andsolidification.

If a sheet of glass, during its transition from the plastic to theSol-id condition, be

cooled more" rapidly from 'one surface than any inequality at one stagebe compensated by an opposite inequality atanother stage.

The above mentioned period of transition starts at the point offormation of the strip and continues to a point in the lehr, and thelength of strip between these two points may be divided into twoportions, that between the point of formation and the lehr, and that inthe lehr itself.

In the following s ecification and the c'laims, the term lehr is used todenote a kiln in which the glass is annealed and is supported on a bed,such a's a series of rollers, adapted to cause the glass to travel fromthe hot to the colder end'. Further, since glass has no definite pointof solidification, it is assumed to be solidified when it has reached acondition in which it can acquire a permanent strain.

According to this invention, the cooling of the upper and lower surfaccsof the strip of glass in the lehr, while in its transition period, iscontrolled, one relatively to the other, in such a manner that, beforethe solidification point of the whole strip is reached, the strip hasbeen symmetrically cooled, whatever may have been the relative amountsof cooling from the two sui-faces of the strip at its entrance to thelehr.

` In the accompanying drawings Figure 1 is a Vertical longitudinalsection,

partly broken away, of a portion of a lehr constructed in accordancewith, and adapted for carrying out, the invention, the said sectionbeing taken on the line l-l of Figure 2 looking towards the left of thatfigure;

Figure is a transverse section of the same on the line 2-2 of Figure 1looking towards the right ot thatligure, and drawn to a scale twice thatto which Figure 1 is drawn, and

Figure 3 is an alternative form of the righthand portion of Figure 1.

The strip of glass 1 rests on the bed of rollers 2 in the lehr 3, theleft-hand end of Figure'l representing the hot end of the lehr. Abovethe strip of glass 1, are three muflies 4, 4 and 5 and below it are fivemuflles 6, 6, 7, 7,.and 8." These muflles are supplied with hot gasesfrom a number of flues, the two top outer nuflles 4,4 being suppliedfrom the flues 9, 9, the top muffle 5 froni the flues 10, 10 and thebottom muffles froni the flues 11.

The top nuffles 4, 5 are heated by gas jets' from agas flue 12 and thebottom mufiles '6, 7 and 8 are heated by gas jets from the gas flues 13.Each flue is provided with air controlling dampers 14 and gascontrolling dampers 18.

At that point in the lehr at which the strip has become solidifiedthroughout, the top mullles 4, 5 are connected to exhaust flues 15, 16respectively, a damper 17 being provided to control the amount of hotgases passing through eachvnuflle.

The bottom muflles 6, 7 and 8 continue to the 'far end of the lehr andare there connected to anexhaust fiue in the ordinary way, these mufliesproviding for the heating of the lehr after the solidification point ofthe glass.

The relative rates of cooling of the upper and lower surfaces of thestrip can be controlled in the above described Construction, by varyingthe pull in the exhaustports 15, 16 and by varying the amount of heatinggases introduced into all or any of the flues 9, 10 and 11.

The control of the said relative rates of cooling and the heating otthelehr after the solidification point of the glass, may be securedin-n1any alternative ways. Thus, the heating of the lehr after thesolidification point may be quite independent of that up to the saidpoint` as shown in Figure 3, where the heat supplied through the ports 9and 10 near the beginning of the lehr and correspondingly reducing thatthrough the ports further down the leh r, or YCO Yersa.

In the length of lehr up to the solidiication point of the glass, anynunber of hot gas supply ports may be provided for both the top andbottom mutlles and, in cases where the ditlerence in the rates ot'cooling of the upper and lower surfaees of the strip is not great, thenumber of inlet ports nay be reduced from that shown, and may differ inthe upper and lower muflles. Thiis, the strip may reach the lehr in suchcondition that sutiieient control is secured by a single inlet port' ineach upper nutlle and by two in each lower mufile, or YCC Yersa.

Since it may result from the treatment of the strip before it reachesthe lehr, that the amounts of cooling of the upper and lower surfaces ofthe strip ditl'er by amounts which are different for the edge portionsfroni what they are for the central portion of the strip.,

a plurality of mufiies preferably are provided either above or below orboth above and below the strip. In the particular Construction of lehrshown in the drawings, three niutiles are shown above and fire below,the heat supplied to the strip by each muflle being independentlycontrollable as described above. By means of this independeutcontrol,the relative rates of cooling of the upper and lower surfaces of thestrip may be controlled so as to he different for portions of the stripnearer the edges from what it is for portions nearer the centre of thestrip.

A similar though less complete difference in control maybe Secured byemploying a plurality of muiles above and a single muflle below or Viceversa.

The supply of heatto the lehr. though preferably etfected by means ofmuliles may be by direct admission of hot gases and the term hot gasesis to be taken to include either gases in a state of con'bustion or theproducts of their combustion.

Having described my mvention, deelare that what I claim and desire tosecure by Let- `ters Patent is':`-

1. Process of cooling continuous glass strip n a lehr n which theproducts of gzseous combuston are ntroduced into portions of the lehrboth above and below the glass strip near the entrance end of the lehr,the amount of heat thcreby supplied to the upper surfaces of the edgeportions of the strip relatively to that supplied to their lowersurfaces being controlled and the amount of heat supplied to the uppersurface of the central portion of the strip relatively to that suppliedto its lower surface being independently controlled, the said controlsbeing to secure symnetrical cooling before the strip solidiiies 2.Process of cooling continuous glass strip in a lehr in which products ofgaseous combustion are introduced into portions of the lehr both aboveandbelow the glass strip near the entrancc end ofthe lehr, the amount ofheat thereby supplied to the upper surfaces of the edge portions of thestrip relatively to that supplied to their lower sui-faces beingcontrolled and the amount of heat supplied to the upper surface of thecentral portion of the strip relatively to that supplied to its lowersurface being independently controlled, the said controls being tosecure symmetrical cooling before the strip solidifie and withdrawingthe said products by flues which are independent for the upper and lowerportions of the lehr.

A lehr for eontinuous glass strip coniprising heating means in the firstportion before the strip solidies, means adapted to control the relativeamount of heat supplied to retard the cooling of the two sut-faces ofthe strip in said portion, and heating means in the latter portionsubstantially independent of the heating means in the said firstportion.

4. A lehr for continuous glass strip comprising a plurality of hot gassupply ports longitudinally of the lehr adapted to supply heat to onesurface of the strip in the first portion ot' the lehr before the stripsolidilies at least one port adapted to supply heat to the other surfaceof the strip before it solidifies, means adapted to control the relativeamount of heat supplied to the two sui-faces, and heating means in thelatter portion of the lehr substantially independent'of theheating meansin the said first portion.

5. A lehr for continuous glass strip comprising means adapted to supplya controllable amount of heat to the upper surface of the strip, meansadapted to supply a controllable amount of heat to the lower surface ofthe, strip and means adapted to control the amount of heat supplied tothe central portion of the strip relatively to that supplied to the edgeportions thereof.

6. A lehr for continuous glass strip comprisingheating means in thefirst portion before the strip solidifies, means adapted to control therelative amount of heat supplied to retard the cooling ofthe twosui-faces of the strip in said portion, means adapted to supply heat tothe portions of the strip nearer to the edge and means substantiallyindependent thereof adapted to supply heat to portions nearer to thecentre of the strip, and heating means in the latter portion of the lehrsubstantially independent of the heating means in the said firstportion.

7 A horizontal lehr for continuous glass strip, comprising mumes on eachside of the strip, means independent with respect to the two sides ofthe strip for introducing hot gases into the mufies and means adapted tocontrol the relative amount of heat so supplied to the mufles on the twosides of the strip.

8. A lehr for continuo'us glass strip comprisng a pluralty of rnuztfiestransversely of the lehr adapted to supply heat to one surface of thestrip before it solidifies at least one muflle adapted to supply heat tothe other surface of the strip and means adapted to control the relativeamount of heat so supplied to the two surfaces.

9. A lehr for continuous glass strip comprising muflles into 'which hotgases are introduced for supplying heat to the first portion of the lehrto retard the cooling of the two surfaces of the strip before itsolidifies, meansadapted to control the relative amount of heat sosupplied to the two surfaces, and heating means in the latter portion ofthe lehr substantially independent of the heating means in the saidfirst portion.

10. A lehr for continuous glass strip comprising muflies adapted tosupply h'eat to retard the cooling of the 'two surfaces of the strip atdiflerent portions thereo'f respectively nearer to the edge and nearerto the centre, and means adapted to control the relative amount of heatsupplied to said dfierent por: tions.

In testimony whereof I have axed my signature hereto.

4 ERNEST BRSTOW LE MARE.

